Een fossiele parel in Nederland

While searching for fossils, in September of the year 1945, in the prae-glacial sands of Sibculo in the province Overijssel,
near the German frontier of Holland, I had the singular good fortune to find a fossil blister-pearl, attached to the inner
surface of a right valve of an Ostrea vesicularis Lam. The pearl and the shell are both of a silicious material. Surrounding
the base of the pearl is a lamellar, crater-like bassin, raised about the diameter of the pearl and smoothly rounded without
and within its rim. The pearl has a diameter of 1 c.m. and is gray in color. A comparative study of the stones in these prae-glaciallayers
proved, the probability that the Sibculo-pearl is a cretaceous boulder of the Quadraten Senoon of Westphalia in Germany. These
observations are the first records for Holland, and the continent of Europe, excepted Sweden.